How about a basic hat? Check out the free patterns page on this site and look for a beginner/intermediate one. You'll have to use double pointed needles when you get to the top of the hat, but once you get the circulars down, dpns aren't bad!

I'm making my maiden circular knitting voyage, too! I'm working on the Quaker Ribbed Bottom Hat, which is on the Free Patterns - Hats page of this site. You don't even need to use DPNs on this pattern!! (That's why I picked it!)